Fluid pressure-powered linear actuators are widely used. They uniformly use some element such as a diaphragm or piston, some part of which moves along a linear axis. It is connected to a valving element. When the pressure changes, the element moves and changes the setting of the valve or whatever else is being controlled or set. Also, conventionally there is a bias spring which biases the element in one direction or the other, and the fluid pressure overcomes this bias in order to move the element. This invention belongs to this art, but provides substantial advantages in reduction of cost, complexity, and envelope size, together with simpler seal arrangements and improved reliability and, greater exerted force generated by a given differential pressure on an element of a given area.